Via structure of printed circuit board

Abstract

An exemplary printed circuit board includes at least a pair of differential vias defined therein, each of the differential vias has an annular ring formed on the PCB, a conductive hole defined in the PCB, and a clearance hole defined in at least one inner layer of the PCB. Each of the clearance holes of the differential vias is oval shaped thus providing a greater area for the clearance holes and needed clearance between vias without creating a superposition zone.

1 . A printed circuit board defining at least a pair of differential vias, each of the differential vias comprising:
 an annular ring formed on an outer surface of the PCB;   a conductive hole defined in the PCB; and   a clearance hole defined in at least one inner layer of the PCB, wherein the clearance hole is oval shaped, and a space is left between the clearance holes of the at least a pair of differential vias.   
   
   
       2 . A printed circuit board comprising:
 at least one outer layer;   at least one inner layer; and   at least a pair of differential vias each comprising;
 an annular ring formed on the at least one outer layer; 
 a conductive hole extending through the at least one outer layer and the at least one inner layer; and 
 a clearance hole defined in the at least one inner layer, wherein the clearance hole is oval shaped, and a space is left between the clearance holes of the at least a pair of differential vias. 
   
   
   
       3 . The printed circuit board as claimed in  claim 2 , wherein the annular ring, the conductive hole and the clearance hole are coaxial. 
   
   
       4 . The printed circuit board as claimed in  claim 3 , comprising two outer layers each of which has formed thereon at least two annular rings corresponding to the at least a pair of differential vias.